Endoscopic surgical instruments are often preferred over traditional open surgical devices since a smaller incision tends to reduce the post-operative recovery time and complications. Consequently, significant development has gone into a range of endoscopic surgical instruments that are suitable for precise placement of a distal end effector at a desired surgical site through a cannula of a trocar. These distal end effectors engage the tissue in a number of ways to achieve a diagnostic or therapeutic effect (e.g., endocutter, grasper, cutter, staplers, clip applier, access device, drug/gene therapy delivery device, and energy device using ultrasound, RF, laser, etc.).
Known surgical staplers include an end effector that simultaneously makes a longitudinal incision in tissue and applies lines of staples on opposing sides of the incision. The end effector includes a pair of cooperating jaw members that, if the instrument is intended for endoscopic or laparoscopic applications, are capable of passing through a cannula passageway. One of the jaw members receives a staple cartridge having at least two laterally spaced rows of staples. The other jaw member defines an anvil having staple-forming pockets aligned with the rows of staples in the cartridge. The instrument includes a plurality of reciprocating wedges which, when driven distally, pass through openings in the staple cartridge and engage drivers supporting the staples to effect the firing of the staples toward the anvil.
Advantageously, the design of the end effector may be such that it can be reused with the surgical stapler. For instance, one patient may need a series of severing and stapling operations. Replacing an entire end effector for each operation tends to be economically inefficient, especially if the end effector is built for strength and reliability over repeated operations. To that end, the staple cartridge is typically configured to be disposable and is fitted into the end effector prior to each operation of the surgical stapler.
An example of a surgical stapler suitable for endoscopic applications is described in U.S. Pat. No. 5,465,895, which discloses an endocutter with distinct closing and firing actions. A clinician using this device is able to close the jaw members upon tissue to position the tissue prior to firing. Once the clinician has determined that the jaw members are properly gripping tissue, the clinician can then fire the surgical stapler with a single firing stroke, thereby severing and stapling the tissue. The simultaneous severing and stapling avoids complications that may arise when performing such actions sequentially with different surgical tools that respectively only sever and staple.
One specific advantage of being able to close upon tissue before firing is that the clinician is able to verify via an endoscope that the desired location for the cut has been achieved, including that a sufficient amount of tissue has been captured between opposing jaws. Otherwise, opposing jaws may be drawn too close together, especially pinching at their distal ends, and thus not effectively forming closed staples in the severed tissue. At the other extreme, an excessive amount of clamped tissue may cause binding and an incomplete firing.
Endoscopic staplers/cutters continue to increase in complexity and function with each generation. One of the main reasons for this is the quest to lower force-to-fire (FTF) to a level that all or a great majority of surgeons can handle. One known solution to lower FTF it use CO2 or electrical motors. These devices have not faired much better than traditional hand-powered devices, but for a different reason. Surgeons typically prefer to experience proportionate force distribution to that being experienced by the end effector in the forming of the staple to assure them that the cutting/stapling cycle is complete, with the upper limit within the capabilities of most surgeons (usually around 15-30 lbs). They also typically want to maintain control of deploying the staples and being able to stop at anytime if the forces felt in the handle of the device feel too great or for some other clinical reason.
To address this need, so-called “power-assist” endoscopic surgical instruments have been developed in which a supplemental power source aids in the firing of the instrument. For example, in some power-assist devices, a motor provides supplemental electrical power to the power input by the user from squeezing the firing trigger. Such devices are capable of providing loading force feedback and control to the operator to reduce the firing force required to be exerted by the operator in order to complete the cutting operation. One such power-assist device is described in U.S. patent application Ser. No. 11/343,573, filed Jan. 31, 2006 by Shelton et al., entitled “Motor-driven surgical cutting and fastening instrument with loading force feedback,” (“the '573 application”) which is incorporated herein by reference.
These power-assist devices often include other components that purely mechanical endoscopic surgical instruments do not, such as sensors and control systems. One challenge in using such electronics in a surgical instrument is delivering power and/or data to and from the sensors, particularly when there is a free rotating joint in the surgical instrument.
Although powered instruments provide numerous advantages, it is desirable to prevent inadvertent firing of the instrument under certain conditions. For example, firing the instrument without having a staple cartridge installed, or firing the instrument having an installed but spent (e.g., previously fired) staple cartridge, may result in cutting of tissue without simultaneous stapling to minimize bleeding. Electronic controls, or interlocks, for preventing powered endocutter operation under such conditions have heretofore utilized active electrical circuits disposed in the end effector for determining whether an unspent staple cartridge has been installed in the end effector. For example, U.S. Pat. No. 5,529,235 entitled IDENTIFICATION DEVICE FOR SURGICAL STAPLING INSTRUMENT to Boiarski et al. discloses an interlock circuit integral to the staple cartridge and having a fuse that is opened responsive to a mechanical force or electrical current applied thereto concurrent with a firing operation. The open electrical state of the fuse is detected via a hardwired control circuit externally located with respect to the end effector to prevent a subsequent firing operation using a spent staple cartridge. In this way, opening the fuse disables the staple cartridge and prevents is reuse.
U.S. patent application Ser. No. 11/343,439 entitled “ELECTRONIC INTERLOCKS AND SURGICAL INSTRUMENT INCLUDING SAME” to Swayze et al. discloses the use of electronic sensors disposed within the end effector for determining if an unspent staple cartridge has been installed. The sensors may include switches connected in series with a motor or other electrically-powered actuation mechanism such that current flow necessary for generating the actuation force is prevented when the staple cartridge is not installed, or when the staple cartridge is installed but spent.
Although the above-described electronic controls are generally effective for preventing inadvertent instrument operation, placement of electronics in the end effector has heretofore required electrical cabling to connect the end effector with other electrical components (e.g., power sources, motors, control circuits, etc.) externally located with respect to the end effector. In cases where such electrical components are disposed within a handle of the instrument (as in the above-described references), the electrical cabling is typically routed via a shaft connecting the end effector to the handle. However, routing electrical cabling in this manner is inconvenient and increases instrument complexity and cost.
In addition to preventing firing of the instrument in the absence of an unspent staple cartridge, it may further be desirable to limit the number of firing operations that may be performed by the instrument.
Consequently, a significant need exists for electronic controls for use in powered cutting and stapling instruments that prevent inadvertent firing (e.g., cutting but not stapling) while avoiding complexities associated with hardwired end effector electronics, and that limit instrument use to a predetermined number of firing operations.